Random fact: Now hear this

by Janie Jones

So we are studying waves now in physics. Which conceptually is pretty cool.

Sound is actually caused by the wave motion of atoms through a medium, such as air, water, or even wood. Sound waves are measured in Hertz (Hz) which is the number of cycles the wave makes in a second. The human ear can hear sound waves in the 20-20,000 Hz range.

The wave motion enters our ear canal and vibrates the tympanic membrane (ear drum), triggering a chain reaction involving the passage of the vibration through the bones in the ear to the fluids in the cochlea. There the waves come in contact with sensory cells that transfer the sound waves to electrical impulses which then travel to our brain and are interpreted as the sounds we “hear.”

“Sound” (bad pun intended) kinda complicated? Well, no one ever said that biology wasn’t an amazing feat of engineering.

Many folks have perhaps heard of ultrasonic sound, which is above the upper limit of human detection. Ultrasound waves are used in the ultrasound machines that allow doctors to see inside a patient’s body, most notably in ultrasound images of the developing fetus, but also are used to shatter kidney stones so that they can be passed “naturally,” and avoid surgery. Some people have heard of “dog whistles” which emit sounds humans can’t hear in the ultrasonic range.

What is less likely known, is that there are many animals that hear sounds in the infrasonic range, or the sounds below the threshold of human hearing. Whales, elephants, some birds, some fish, and octopi and squid all can hear infrasonic sounds. What’s more, elephants and whales are known to communicate with each other using infrasonic sound.

Well, now, that was random and interesting, wasn’t it?

Try listening to a physics lecture on the subject, it just might make your ears “hertz.”